I think the best way to help with the (current) game's replayability (for me) is to allow for more diverse builds to be competitive.
Be it skill issue or whatever I feel like I never do anything with the Pressure stacking, which a big term for it considering there's only two cards related to it (No Pulling Out, Flash of Skin).
I think it would be great for every run to feel like I'm going in not knowing what I will end up building my deck like, instead of it ending up being about drawing a billion cards and stacking a lot of Lucky and winning that way. That's how every run has felt to me for now. I remember I used to do some Pity stuff when Preparation was how it was originally (I'm not saying it should come back, or not), and I feel like Pressure could become a more prominent mechanic of Moira.
That way there would be at the very least three ways to build a deck: Lucky stacking, Pity stacking, Pressure stacking.
I'm not sure if that would be enough however, maybe there's just not that many cards and that's also part of the issue? Since you end up pretty much seeing all the cards every run? Having maybe 10 or 20 more could add for way more variation?
Since we're here, I would also like to mention that I feel like the "Poison" mechanic is a bit too slow and even on the Corruption Level that shortens it by 2, even without Incense it still feels like I'm completely free to move around the map however I want, going back and forth completely abusing the always available Shop of each floor.
I don't know if I would say that the Poison should be necessarily faster, but maybe it should accelerate instead? maybe after the first trigger it becomes one meter/unit shorter, restarting on each Floor? Allowing you to move around at the start, but then pushing you off into taking more risky decisions? Maybe that should be the Corruption Level's effect rather than it being the default new behaviour?
Aside from all that, could I ask for maybe a way to export run data? Like Card Reward choices, Events encountered and Options taken, Toys acquired, maybe even upgrades (cards and toys), Damage taken, etc etc... For personally looking more in-depth at the numbers and statistics I could come up with on my own. Or maybe just the possibility to mod the game in such a way that I can obtain this data myself, since the game doesn't expose it's .pck and I don't think it's possible to do anything about that on my own.
I think that's all I can think of right now, in general, I love the game a lot and can't wait to see how it evolves over time... <3